Voltage drops across the entire system

[WLC]

I should add the regulator is also 14.5V and new, fitted by the company who did the bearings so it may be a cheap and nasty one as its reading low, any reccomendations for better quality 14.5v regulators greatfully recieved

Take it back

[ghost123uk]

I wonder how long you let the van idle for before you took these measurements?

About 5 to ten minutes.

What was the state of charge

12.6 on the starter (which is less than a year old, good make and has never been flattened, spins the starter fine, but always sits at 12.6 Volts)

12.6 Also on the Leisure, also nearly new, never flattened, after a good charge and a rest, this one sits at 12.9 Volts.

how much do you use it?

Daily.

When did you last charge or trickle charge the battery?

Months ago for both batteries, my bad I know, though the solar is wired up all the time, but mine produces virtually nothing in dull conditions (< 100 mA) but read on...

I don't need to tell you that If there is any significant charging current the resistance of the wires will give volt drop

I strongly suspect this is the case. I had not expected a battery pulling a charge ( of ? Amps) would drop so much voltage down those thick, seemingly good condition cables. But, it is this reason why I tell folk on here to measure their starter battery charging Voltage after a drive, or at least after a few minutes ticking over, so the initial drain and replenishment caused from starting the van is negated. Today I will be making some current measurements and setting up my poor man's Sterling type charging system, read on....
.

Immediately after start up and after the split charge relay connected I saw about 13.1V on the leisure batt voltmeter but it soon climbed after a few minutes to the figures below presumably because it was well charged so the current flow soon dropped off

Yes, my results have GOT to be current flow dropping the voltage ( I knew that and I know you know I knew that ) but as said above, I was suprised by the amount of drop in thick, seemingly good condition cables. ( could get out my super accurate Avo, which has a very low resistance scale, measure the resistance from Alt B+ to Batt B+ and work it out (Ohms law of course) but I ain't going to go that far. I just need a better system, I don't think I need the maths to prove it

I suspect my drop from alt to batts is mainly due to ignition current, as I rev this voltage drops a little as the coil draws more current.

Aye, that and some current going into the battery.

I should add the regulator is also 14.5V and new, fitted by the company who did the bearings so it may be a cheap and nasty one as its reading low

Similar here. Today I will test for voltage drop at the Alt B+ under headlight load to see how well the regulator regulates the output of the alternator. I suspect I am going to be posting somewhat disappointing results, we shall see.

any recommendation for better quality 14.5v regulators gratefully received

Same here.


####################################################################

I tried out my idea yesterday and today I will be wiring it in properly because it looks like it will work just fine.
Output of split charge to the inverter (so it comes on as soon as engine running)
Inverter feeds a 10 Amp "Smart" charger.
Smart charger is connected to the leisure battery.

This obviously achieves the advantageous results one gets from the standard method of using a smart charger occasionally. I will I think stick with using the (decent quality) croc clips and std 13A mains plug, that way I can still use the smart charger in other environments without having to un-wire it all. Or I might hard wire it

I reckon that, as I use my leisure battery very often, especially in winter to power the Propex for early morning warmth, plus the fact that I often sleep in the van and use lights, laptop, radio etc, that my leisure battery is nearly always requiring a charge to some extent and it is likely that which produced my low-ish Voltage results in the OP.

Some full "smart" charging will be going on today, then some more Voltage measurements (when I bet I will get results similar to yours Itchy), then some re-wiring to accommodate the inverter / smart charger system.

It's a murky day here and I'm not in work today, so what better way to fill a dull day

[WLC]

I strongly suspect this is the case. I had not expected a battery pulling a charge ( of ? Amps) would drop so much voltage down those thick, seemingly good condition cables.

Count the number of connections between the alternator and each battery John

You get a voltage drop at each connection

Two Golden Rules for You :-

Connect direct - reduce voltage drop

Use oversize cable / wire - reduce voltage drop
.

[ghost123uk]

Thanks for the input WLC, but a couple of things to note, as per my OP, there is no problem here, I am just "playing" / improving things. Also (and I know you wouldn't know this of course) I have been a professional electronics engineer and Amateur Radio operator for many years, so fully understand the subject. This thread is more for "pub like" discussion and swapping ideas. I like Mocki's idea of putting the starter battery in the engine bay (as per Diesels) and using the old wiring at the drivers seat for the leisure and up front feed Seems very sensible, but for now I am going to try my poor man's Sterling solution and see how that goes.

p.s. As this is a forum and sometimes the "intent" behind the written word can be misinterpreted, plus you are quite new here, note:- my comments above are not meant to be disparaging.


p.p.s. = When I am making any connections on heavy gauge wire, I interlace the ends, bind with single strand copper wire, generously solder, then at least 3 layers of heat-shrink (each layer getting shorter) for safety and to reduce bending loads at the ends of the soldered join. It is very unlikely that any resistance (and resulting voltage drop) could occur on a join like that. I made a "one in to four out" loom in a similar way (for the 4 items in my vans that require a hefty-ish current) though a decent quality insulated "bus bar" arrangement would be easier, if I could find one.

[itchyfeet]

 I had not expected a battery pulling a charge ( of ? Amps) would drop so much voltage down those thick, seemingly good condition cables

I think thats what is missing, what current is your leisure still pulling after 5 to 10 miniutes when that voltage is low?
Will try to measure mine also.

[CovKid]

Would be good if my starter battery was also in engine bay. Only thing that put me off that idea is in freezing cold weather - won't its potential drop off the lower the temperature? If not, thats where its going!!

Access another issue though - particularly if you needed a jump start... I'd have to fit some sort of flylead job. Be a right pain having to get stuff out the back and lifting engine hatch.

[what2do]

I know ctek sell short leads that can permanently bolted to the battery terminals and have a push connector at the other end so that you can easily remove the charger unit to use it elsewhere.

[WLC]

Would be good if my starter battery was also in engine bay. Only thing that put me off that idea is in freezing cold weather - won't its potential drop off the lower the temperature? If not, thats where its going!!

Access another issue though - particularly if you needed a jump start... I'd have to fit some sort of flylead job. Be a right pain having to get stuff out the back and lifting engine hatch.

http://www.ebay.co.uk/sch/Vehicle-Parts ... c=50&rt=nc" onclick="window.open(this.href);return false;
.

[WLC]

Would be good if my starter battery was also in engine bay. Only thing that put me off that idea is in freezing cold weather - won't its potential drop off the lower the temperature? If not, thats where its going!!

Access another issue though - particularly if you needed a jump start... I'd have to fit some sort of flylead job. Be a right pain having to get stuff out the back and lifting engine hatch.

Another option to you is to sort things so you can jump off your house battery.

[ghost123uk]

 I had not expected a battery pulling a charge ( of ? Amps) would drop so much voltage down those thick, seemingly good condition cables

I think thats what is missing, what current is your leisure still pulling after 5 to 10 minutes when that voltage is low?

Well 30 minutes ago, I fired it up. Voltage at starter was 13.76V. Looking at it ten minutes ago it had risen to 13.92V So it looks like mine is behaving pretty much like yours Itchy (so it was just a charging load dragging it down)

By the way, and to answer your question Itchy, after that 20 minute tickover, the feed to the leisure battery was at 13.6 volts and the input current was only 2 amps. I then tested it with my smart charger (off "real" mains) and got 14.44 Volts and 6 Amps going in, so my "poor man's Sterling like" system should work well

However, I now have turned it off and have my (new) Smart Charger (running conventionally off a mains extension lead) charging the starter battery. When that is complete I will do likewise with the leisure battery. Then I will wire it all up as per my "poor man's Sterling" arrangement and see how it goes.

Great fun

E D I T = Punctuation OCD !

[WLC]

Would be good if my starter battery was also in engine bay. Only thing that put me off that idea is in freezing cold weather - won't its potential drop off the lower the temperature? If not, thats where its going!!

Access another issue though - particularly if you needed a jump start... I'd have to fit some sort of flylead job. Be a right pain having to get stuff out the back and lifting engine hatch.

A third option is to run everything except the starter motor off the leisure battery

The snag here is that you either have to run the ignition off the starter battery, or arrange to hot wire the ignition from the start battery if you've got a flat leisure battery

Obviously if the start battery only runs the starter the chances of a flat battery are very very low
But poo happens
Your choice
.

[WLC]

Well 30 minutes ago, I fired it up. Voltage at starter was 13.76V. Looking at it ten minutes ago it had risen to 13.92V So it looks like mine is behaving pretty much like yours Itchy (so it was just a charging load dragging it down)

Great fun

What was the voltage at the alternator post (post please not the lug) when the voltage at the starter solenoid was 13.76 please
.

[itchyfeet]

what about when the leisure is very flat, won't an alternator provide more charging current than your mains charger can so charge quicker ( assuming you upgrade that cable)?

Personally I think split charge relay in the engine compartment and a fat cable to the leisure.

[WLC]

what about when the leisure is very flat, won't an alternator provide more charging current than your mains charger can so charge quicker?

Spoil sport
.

[ghost123uk]

what about when the leisure is very flat, won't an alternator provide more charging current than your mains charger can so charge quicker?

Initially maybe yes, I have found though that the alternator charge to a "flat" (say 11.5 Volt) battery might go up to around 20A or a bit more even, but within a couple of minutes (literally) has dropped to well below that as the batteries internal Voltage ("PD") rises to closer to the charge voltage. A smart charger like mine might only have a 10A max output, but it will maintain that 10A for longer and the other "smart" features will, I reckon, work to my advantage overall. I have a high confidence it will make my leisure battery work better. Time will tell